“Even the technical sense of ‘environment’ used in quantitative behavioral genetics is perversely confusing. Now, there is nothing wrong with partitioning phenotypic variance into components that correlate with genetic variation (heritability) and with variation among families (‘shared environment’). The problem comes from the so-called ‘nonshared’ or ‘unique environmental influences.’ This consists of all the variance that is attributable neither to genetic nor familiar variation. In most studies, it’s calculated as 1 – (heritability + shared environment). Practically, you can think of it as the differences between identical twins who grow up in the same home. They share their genes, parents, older and younger siblings, home, school, peers, and neighborhood. So what could make them different? Under the assumption that behavior is a product of genes plus environment, it must be something in the environment of one that is not in the environment of the other.

“But this category really should be called ‘miscellaneous/unknown,’ because it has nothing necessarily to do with any measurable aspect of the environment, such as one sibling getting the top bunk bed and the other the bottom, or a parent unpredictably favoring one child, or one sibling getting chased by a dog, coming down with a virus, or being favored by a teacher. These influences are purely conjectural, and studies looking for them have failed to find them. The alternative is that this component actually consists of the effects of chance – new mutations, quirky prenatal effects, noise in brain development, and events in life with unpredictable effects.

“Stochastic effects in development are increasingly being recognized by epidemiologists, frustrated by such recalcitrant phenomena such as nonagenarian pack-a-day smokers and identical twins discordant for schizophrenia, homosexuality, and disease outcomes. They are increasingly forced to acknowledge that God plays dice with our traits. Developmental biologists have come to similar conclusions. The bad habit of assuming that anything not classically genetic must be ‘environmental’ has blinkered behavioral geneticists (and those who interpret their findings) into the fool’s errand of looking for environmental effects for what may be randomness in developmental processes.“

did you get that?: “The bad habit of assuming that anything not classically genetic must be ‘environmental’ has blinkered behavioral geneticists (and those who interpret their findings) into the fool’s errand of looking for environmental effects for what may be randomness in developmental processes.”

“The heritability of behavioral traits is typically on order of 50%. However, what’s left (after you subtract the ‘shared environment’, which is generally 0, but more on that soon) is just the ‘unexplained variance.’ We don’t know what that is. Much of it, perhaps a good deal, is measurement error. Evidence suggest that that is actually missed heritable influence.

“However, what’s left over, after you’ve accounted for ‘attenuated heredity’ may be what’s known developmental noise. This is ‘environmental’ in the sense that it’s not inherited, but is essentially random and not subject to controlled manipulation.

.“Even developmental noise appears to heritable, to a degree. Whether or not this is ‘on purpose’ or an evolutionary accident is unclear.

“And finally, and this is an ‘advanced’ topic, impact of the ‘unique environment’ – what makes identical twins raised together different from one another – could itself significantly genetic in nature, because identical twins aren’t actually genetically identical, but have different de novo mutations.

“You see why I’m a little hard on the ‘nurturists’ out there. Broadly, the evidence has not been kind to ‘environmental’ influences. Note that this is not to say that they don’t exist.”

there’ll be more on this — much more i’m sure — coming down the pipeline. in particular, watch this space (jayman’s blog!) for a more detailed explanation of all this — coming soon! (^_^)

He really gets into how we know heritability estimates are higher than typically reported (that popular 50-50 nature/nurture meme):

So, what does the “new” research from the 1980s, that is now finally beginning to reach public awareness, tell us about human nature? The most obvious part is that nature is a major factor. This is typically summed up in textbooks in the 50/50 rule, claiming that genes and environment can explain about half of the variance each of things like intelligence, personality, psychopathology etc. Which is easy to remember – but also incorrect. This is due to the fact that there is something called measurement error. Most studies are done in a way that doesn’t distinguish this error from the environmental factor. So it’s 50 percent nature and 50 percent environment plus measurement error. Studies that have managed to minimize measurement error typically yield heritabilities for personality traits and similar characteristics around 70 percent. You also have the fact that some of the traits linked to the most important life outcomes, like intelligence and impulsiveness, have even higher heritabilities, around 0.75-0.80.

Traits not subject to much measurement error, like BMI or height, consistently yield heritabilities in the 0.75-0.8 range. Even many common mental disorders (e.g., ADD, schizophrenia) have heritabilities in that range.

Also key here, and when you think about it, the single strongest blow to the notion that environmental influences matter much is the 0 shared environment. The fact the effect of growing up in a certain home is consistently zero is a major clue that something is up there.

As well, over there I talk about something that gets little discussion, but may be phenomenally important, as mouse studies are indicating:

And finally, perhaps most poignant of all, but greatly underrated, is the fact that that identical twins are not actually genetically identical, but possess subtle differences due to de novo mutations. While behavioral geneticists and others like to ignore these, identical twins are our metric of the effects of heredity. We think we can precisely measure the genetic effect vs “environmental” one by looking at identical twins raised together – anything different between them must be due to environment, so the story goes. But the differences between them could be due to genes, so in reality, we have no idea how big the effect of the “environment” truly is.

These differences are starting to recognized as being potentially powerful, as seen from the differences of supposedly (but not truly) genetically identical mice:

Genetic tests that can distinguish between identical twins are becoming availible. This is an underappreciate goldmine in future research into genes and environment.

There’s a dude over at Steve Sailer’s that was trying to argue with me about this key point. He’s trying to claim that since most mutations are of neutral effect, we can ignore these subtle genetic differences between identical twins. Well, the mouse studies indicates that we can’t. Tiny genetic differences can lead to large differences in expressed traits. This has practical significance up and down the board. For one, it does cast into question the wisdom of assuming twins are perfect genetic control in observational studies (as I said to Staffan, the genetic confound never goes away).

All this does limit the effect that deliberate environmental modifications can possibly have on expressed traits (my notes about the grand scale environment of the day notwithstanding). Yet, people, even in the HBD-sphere, continue to believe in the effect of nuture, to an extent. Even the “naturists” are “nurturists”. There are reasons for this, which I will expand upon in a future post, but to me, it doesn’t seem prudent to pick and choose the parts of science you like or which fits your narrative/view. You have to take the whole thing for what it says.

if evolution is in a race with bugs and needs a minimum amount of change to allow selection to work then in a population that is already adapted to its environment and therefore has weak selection maybe randomly switching traits on and off provides the raw material needed to work with?

Jayman – “Yet, people, even in the HBD-sphere, continue to believe in the effect of nuture”

Well, there is one long-term effect of good nuture that I think is very important: the memories of a happy childhood! Happiness counts. I’m not sure what else does — success? Only if it makes you happy. We should love our children not because this will make them turn out better. We should love them because it feels good. Feels good to be loved too of course.

@ JayMan: amen, brother – spot on. we used to use the examples of the same seeds being planted in fertile soil vs. bad soil, & the japanese rise in height after WW II, etc. to explain why highly heritable traits were very mutable. But, more than that – our genes allow us to be adaptable enough to deal effectively (in varying degrees) with whatever the environment is throwing our way – & a lot of what the environment throws our way was influenced by our or others genes. i liked that comment you linked to – bravo! especially good comments considering you are probably not yet getting to sleep thru the night (spoken as a parent of grown children:)

from my understanding, it seems more like it’s: heredity…plus maybe more heredity (affecting the developmental noise?)…plus noise…plus the environment a bit…and not really epigenetics at all (not from an hereditary point-of-view anyway).

Intelligence and personality are not ”the genes” but a combination with many genes, i believe, which result in a full-phenotype. We, as adaptative beings, have polygenic genes which contribute to our contextual ‘ambientation’. I believe that we have many but not all, genes and it varies individually.
The most important key, my capacity of adaptation depend only of my genes, there a limit. I could be more extrovert, but ”John” will can much more than me. What the ”environmentalists” call of ”environment” i call of ”internal polygenic variation”. Is not, the environment make me change to adapt, but am i that make the best ‘choice’ based on my ”internal possibilities”. I could be more extrovert but not more than John. I could be more extrovert but not more than ”athletes” or ”comedians”.
Environment is exactly equal to ”lamarckism”, i can’t increase my height if i stretching my neck to pick fruit in the trees, but if I have mutations to gigantism and I’m a teenager, so I will can.
Verbal iq people ”prefer” study ”verbal things”, it is only the adaptation to best choice to take the better internal weapon-genes to compete. If i’m not higher math intelligence i’m not choice. Evolution is like a silent battle.

OK, so now I’m even more confused. Does Pinker now accept that the black-white IQ difference is genetic? As of The Blank Slate, he didn’t, writing “My own view, incidentally, is that in the case of the most discussed racial difference–the black-white IQ gap in the United States–the current evidence does not call for a genetic explanation… For many reasons, the experience of African Americans in the United States under slavery and segregation is not comparable to those of immigrants or rural isolates, and their transition to mainstream cultural patterns could easily take longer.”.

That sounds an awful lot like an environmental explanation to me. Maybe he’s changed his mind on that, but as recently as 2006, he was saying that he doubted the Ashkenazi IQ was the result of genetics.

So if he doesn’t think it’s genetic, and he doesn’t think it’s environment, is he saying that these differences, which are highly stable over time, are the result of random statistical noise?

@Anonymous
Not all differences between population are gene-based. Jensen in his “the g factor” in fact as an example put his own analysis of deep-south black iq with whites, where he had shown that in the deep south the large part of iq difference were not gene-based (and the same analysis led him to conclusion that outside deep south, iq difference has to be at least partially genetic)

Damn, I type too fast and I produce too many errors.
“In fact Jensen in his “the g factor” as an example put his own analysis of deep-south black iq DIFFERENCE with whites, where he had shown that in the deep south the large part of iq difference WAS not gene-based

well, yeah – if there are extremely different “environments” (those environmental differences – coff – are created to a large degree by genetics – coff) but again – if there are widely different environments – e.g., one group has terrible “schools” the other has great schools, etc. – then a lot of the difference between the groups will show up as “environmental” — whereas if everyone has the SAME environment – ALL the differences left are GENETIC.

“if there are widely different environments – e.g., one group has terrible “schools” the other has great schools, etc. – then a lot of the difference between the groups will show up as “environmental” — whereas if everyone has the SAME environment – ALL the differences left are GENETIC.”

OK, but who is actually claiming that the environments of blacks and whites in America are “widely different” (at least anymore)? Who would claim that Ashkenazi Jews in America or Europe have widely different environments than their neighbors?

Do you think he’s just being dishonest to keep his job here, or does he really not believe it? Or does he think that the differences really don’t have to be all that wide?

i think about everyone in the US has a stimulating environment from birth on – but disingenuous types a la Pinker say “well yeah maybe IQ in whites is fairly genetic – & maybe IQ in [insert any group here] is fairly genetic – but certainly the mean IQ differences between those groups can’t be genetic!” when that would be a logical person’s first guess :) then they come up with some grandiose environmental non-occam’s razor-ish mumbo jumbo instead of saying “yeah, i guess it would make sense those mean group IQ differences would be mainly due to genetics.” they don’t want to admit that – they’ll only step up to the bridge but they won’t cross it!

“OK, so now I’m even more confused. Does Pinker now accept that the black-white IQ difference is genetic? As of The Blank Slate, he didn’t, writing ‘My own view, incidentally, is that in the case of the most discussed racial difference–the black-white IQ gap in the United States–the current evidence does not call for a genetic explanation… For many reasons, the experience of African Americans in the United States under slavery and segregation is not comparable to those of immigrants or rural isolates, and their transition to mainstream cultural patterns could easily take longer.’

That sounds an awful lot like an environmental explanation to me. Maybe he’s changed his mind on that, but as recently as 2006, he was saying that he doubted the Ashkenazi IQ was the result of genetics.

So if he doesn’t think it’s genetic, and he doesn’t think it’s environment, is he saying that these differences, which are highly stable over time, are the result of random statistical noise?”

Make no mistake, Steven Pinker is a very smart man. There’s a reason he was one of first people in (what is effectively) HBD that I’ve admired. I think, yes, he’s saying what he needs to say to keep his job and hence, visibility, where, I think he does much more good than harm, even if he is forced to put out obviously self-contradictory claims like these. He’s walking a very tight line between speaking the truth and keeping his career. This isn’t the first time he’s let hints of the truth slip out:

[…] the “unexplained variance” – the difference seen identical twins raised together (see it’s not nature and nurture… | hbd* chick). This is an untapped avenue of research that remains to be explored. Now if we could only get that […]